4663 The Journal of Experimental Biology 209, 4663-4675 Published by The Company of Biologists 2006 doi:10.1242/jeb.02581
Lipid remodeling in wild and selectively bred hard clams at low temperatures in relation to genetic and physiological parameters Fabrice Pernet1,*, Réjean Tremblay2, Chantal Gionet1 and Thomas Landry3 1
Institut de Recherche sur les Zones Côtières, 232B rue de l’Église, Shippagan, Nouveau-Brunswick, E8S 1J2, Canada, 2Institut des Sciences de la Mer, 310 allée des Ursulines, Rimouski, Québec, G5L 3A1, Canada and 3 Department of Fisheries and Oceans, Science Branch, Gulf Fisheries Centre, PO Box 5030, Moncton, New Brunswick, E1C 9B6, Canada *Author for correspondence (e-mail:
[email protected])
Accepted 4 October 2006
Summary response of the phospholipid to sterol ratio as well as in A temperature decrease usually induces an ordering levels of 22:6n-3 and non-methylene interrupted dienoic effect in membrane phospholipids, which can lead to fatty acids. Hard clams showed an increase in 20:5n-3 as membrane dysfunction. Poikilotherms inhabiting temperature decreased, but this was not maintained eurythermal environments typically counteract this during overwintering, which suggests that 20:5n-3 may temperature effect by remodeling membrane lipids as have been used for eicosanoid biosynthesis as a stress stipulated in the homeoviscous adaptation theory (HVA). response to environmental conditions. Selectively bred Hard clams, Mercenaria mercenaria, can suffer high hard clams were characterized by a higher metabolic overwintering mortalities in the Gulf of St Lawrence, demand and a deviation from Hardy–Weinberg Canada. The selectively bred M. mercenaria var. notata equilibrium at several genetic loci due to a deficit in can have higher overwintering mortalities than the wild heterozygote frequency compared with wild clams, which species, thus suggesting that the two varieties have different degrees of adaptation to low temperatures. The is believed to impose additional stress and render these animals more vulnerable to overwintering mortality. objective of this study was to investigate the changes in Finally, an intriguing finding is that the lower metabolic lipid composition of soft tissues in wild and selected hard requirements of wild animals coincide with a lower clams in relation to their metabolic and genetic unsaturation index of their lipids, as predicted by characteristics. Clams were placed at the northern limit of Hulbert’s theory of membranes as pacemakers of their distribution from August 2003 to May 2004; they metabolism. were exposed to a gradual temperature decrease and then maintained at
